Deciding how to review and permit for structures with three or more units can be complicated. This article will provide Building Code-driven direction on making the distinction between these structure types, how to review them, and permit for them. Deciding how to review and permit for a structure depends on the structural configuration – this is key.
Terminology - what is it called
'Triplex' and 'four-plex' are real estate and developer terms, not technical code terms. Other commonly used real estate and developer terms include duplexes, rowhouses, condominiums, condos, quadplexes, five-plexes, and so on.
None of these terms exist in the Oregon Building Code or in the technical code world.
Townhouses
First, let's look at a portion of the Oregon Residential Specialty Code (ORSC) and how it defines townhouse:
The provisions of this code shall apply to the construction, alteration, movement, enlargement, repair, equipment, use, occupancy and location of the following:
1. Detached one- and two-family dwellings and townhouses classified as Group R-3, and accessory Group U Occupancies, not more than three stories above grade plane in height.
[RB] TOWNHOUSE. A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from foundation to roof and with a yard or public way on not less than two sides.
If the 'triplex' or 'four-plex' meets the definition of townhouse, then it is covered by the ORSC scope of application and would be permitted as such. Ultimately, the actual structural configuration will dictate the appropriate code application.
Here are some examples of townhouses:
While these may all be commonly referred to as 'triplexes,' they each have three or more attached units, and each unit appears to be sparated from foundation to roof, with a yard or public way on at least two sides. As such, these would be regulated by the ORSC as townhouses. Townhouses are only limited in number by land use, and not by the ORSC.
Townhouses are not considered 'multifamily.' Each townhouse is a separate dwelling unit, often individually owned, and considered a separate building for the purposes of ORSC application. Shared elements are permitted as detailed in ORSC Section R302.2.
Multifamily structures
In the illustration below, both buildings have three units. The building on the left has a unit in the basement, and the building on the right has a unit on the ground floor. These buildings will commonly, but incorrectly, be referred to as 'triplexes', but they do not meet the definition of a townhouse because the unit separation does not extend from foundation to roof, causing unit 'stacking'.
From a relative hazard consideration, having stacked units statistically presents a higher level of assumed hazard than having only adjacent units separated from foundation to roof. As such, the buildings above would be regulated as multifamily Group R-2 apartments under the Oregon Structural Specialty Code (OSSC).
If the design of a residential building includes stacked units and does not meet the townhouse definition, it will be regulated by the OSSC and permitted as a Group R-2 multifamily apartment.
The exception to this is detached two-family dwellings, commonly incorrectly referred to as 'duplexes'. Two-family dwellings may be stacked or side-by-side, and the relative hazard is mitigated by the limitation of two total units being physically connected.
The biggest differences in the R-2 application are possible accessible design requirements (covered multifamily dwellings, as defined) and an automatic fire sprinkler system per OSSC Chapter 9.
310.3 Residential Group R-2.
Residential Group R-2 occupancies containing sleeping units or more than two dwelling units where the occupants are primarily permanent in nature, including:
Apartment houses
[…]
Conversions, covered multifamily dwellings and the scope of the law
With the passage of House Bill 2001 in 2019, 'duplexes,' 'triplexes' and 'quadplexes' may become much more common throughout the State. Considering the conversion of a large existing dwelling into two-, three- or four-unit multifamily apartments, these rules may help delineate the existing code application and subsequent permitting path.
Of note:
(4) Applicable standards for the conversion of a single-family dwelling as follows:
(a) A conversion into
two dwelling units follows the construction standards of the Oregon Residential Specialty Code (ORSC); and
(b) A conversion into
three or four dwelling units follows the construction standards of the Oregon Structural Specialty Code (OSSC).
Finally, we have the scope and application of the Fair Housing Act, as set forth by ORS 447.220. This scope applies to covered multifamily dwellings as defined in the FHA, statute, and OSSC:
COVERED MULTIFAMILY DWELLINGS. See ORS 447.210(5).
ORS 447.210(5) is not a part of this code but is reprinted here for the reader's convenience:
447.210 Definitions.
(5) "Covered multifamily dwellings" means buildings consisting of
four or more dwelling units if such buildings have one or more elevators, and ground floor dwelling units in other buildings consisting of four or more dwelling units. Dwelling units within a single structure separated by firewalls do not constitute separate buildings. […]
The trigger for 'covered' units is a first-occupancy having four or more dwelling units in a single building. Often, this is why developers prefer to build new 'triplex' multifamily units, staying beneath the covered multifamily dwelling threshold.
Regardless of the reasoning, the actual structural configuration of a 'triplex' or 'quadplex' – either a townhouse or multifamily housing – dictates the appropriate permitting path and necessary Certificate of Occupancy requirements.
How to permit for townhouses and multifamily structures
For
townhouses, create a
Residential Structural record type to start, with Townhouses as the Category of Construction. Townhouses are considered separate individual dwelling units (and often individually owned) for the purposes of code, even though they appear to be a single building. Ideally, there should be one record for each attached unit, to keep inspections and occupancy most organized.
For
multifamily structures, create a Commercial Structural parent record for each individual building, not each unit, noting the number of dwelling units the building contains.
As the project progresses, whether classified as townhouses or a multifamily structure, each Structural Parent Record would have related Child Records for the Mechanical, Electrical, and Plumbing records. It is important to relate all the individual attached unit records together to keep the project expiration dates synchronized and the contiguous structure all connected.
These MEP records can be cloned as the same base record number, or copied and related after-the-fact as separate record numbers, based on preference and how the records were submitted. See the following articles for more information: